In order to facilitate the reading of the description to follow, a number of terms and acronyms are defined below:
The term “camera” refers herein to a device, system or facility that captures a 3D reality/object and transforms it to a series of images. Nowadays producing images from a 3D object can be carried out by a variety of means, such as a radar signal, an infrared camera or a video camera. The images are referred to herein as “frames”.
The term “vehicle” refers herein to any type of object that is guided by an inner guidance sub-system. Examples for such vehicles: a car, aircraft, satellite, torpedo, missile, ship, etc.
The term “automatic guiding system” refers herein to a system for guiding a vehicle towards a target object or area. In order to carry out this operation, the vehicle comprises a camera. Images captured by said camera are conveyed to a control center and presented on a display. By guiding the vehicle, or marking a target point or area on a displayed image, and by conveying the information relating to said marking of the vehicle, the vehicle's control mechanism (referred herein as “inner control loop” or “inner guidance sub-system”) directs the vehicle's steering system to move towards the target point.
The term “operator” refers herein to a human being or automatic means (i.e., a computerized system) that makes the decisions as to what point or area to guide the vehicle. Concerning manual operation, the pointing can be carried out by a device (such as computer mouse, joystick, touch screen, and so forth). Concerning automatic means, neither a display nor pointing device is required, since an automaton can manipulate data without the intermediation of a display or pointing means.
Generally, in vehicle guiding systems that involve the transfer of images from the vehicle to a control center, the image signal is compressed in order to reduce the bandwidth required for transmission.
FIGS. 1, 2a, and 2b schematically illustrate a typical system for remotely guiding a vehicle by a human operator, according to the prior art.
At the vehicle 10: frames captured by camera 11 are compressed by a compressor 12 (generally a software/hardware component) and transmitted via transmitter 13 to the control center 20. The transmission from the vehicle to the control center 20 is referred to herein as “Downlink”.
At the control center 20: the transmission is received by a receiver 21, decompressed by decompressor 22 (generally a software/hardware component) and the frames are displayed on display 23.
The operator 24 uses a pointing device 25 (such as a mouse) to mark on the screen 23 the target point to which the vehicle should be guided. The coordinates of the marked point are transmitted to the vehicle via transmitter 26 of the remote control center. The transmission from the control center to the vehicle is referred to herein as “Uplink”.
Back at the vehicle the receiver 14 receives the control commands transmitted from the control center 20 and feeds them to the inner guidance sub-system 15. The inner guidance sub-system 15 further comprises a tracker or a navigation system (or both) 151 and a steering system 152 which directs the vehicle towards a certain point.
Compressing and decompressing of images is carried out in order to reduce the amount of the transferred data, and to suit the restrictions of a narrow-bandwidth communication channel.
The system described in FIGS. 1 and 2 consists of two control loops:    a. The inner control loop, on which the steering sub-system of the vehicle guides the vehicle to a defined target point.    b. The outer control loop, which comprises the downlink transfer to the operator and the uplink transfer of data from the control center to the vehicle.
The outer loop consists of the following stages:    a. The Sampling stage of the vehicle, in which the camera captures the images;    b. The Compression stage of the vehicle, in which the frames are compressed in order to reduce the amount of data;    c. The Downlink route, in which the compressed frames are transmitted to the control center;    d. The Decompression stage of the control center, in which the frames received at the control center are decompressed and displayed to the operator on the display;    e. The Pointing stage, at which the operator may (but need not) define a new target point; and    f. The Uplink route, in which the coordinates of the new target point are sent to the vehicle.
The inner loop at the vehicle adjusts the steering system of the vehicle to move towards the target point.
If the operator marks a new target point, then:                The coordinates of the new target point are transmitted from the control center to the vehicle via the uplink;        The inner loop mechanism adjusts the steering system to the new target point, and the vehicle is guided towards this target point.        
Certain factors may cause a lag between the time an image is captured by the camera and the time the same frame is presented on the display at the remote control-center.
A major reason for this lag may be associated with the downlink bandwidth allocated for transferring the images. If the bandwidth is not wide enough, the use of compression techniques may be required. These techniques may involve skipping frames or using bidirectional estimation (referred to as B frames in the compression standards such as ISO 13818-2 (MPEG2-video). The lag between the captured frame and the displayed frame is inherent to both techniques. In general, video (or image) compression produces bits at a variable rate. Transferring these bits via a fixed bit-rate channel requires buffering (at both ends of the channel), and thus results in additional lagging.
There may be other obstacles that contribute to the lag, for example, when the communication path is made via relay stations, telephone lines, modems, Internet protocols, and so forth. The lag may appear in the downlink route, as well as in the uplink.
Due to this lag in displaying the image at the control center, the operator cannot deal with up-to-date displayed images. Moreover, until the coordinates of the marked point reach the vehicle, additional lag is created, and the vehicle is no longer at the position apparent to the operator when marking the target point.
A partial solution to this problem, as presented in the prior art, is the expansion of the bandwidth. In this way, a higher rate of transferred data between a vehicle and a control center can be obtained. However, the drawback of this solution is the exhausting of bandwidth resources. Due to the bandwidth restrictions, different solutions are required. Moreover, this solution, when applied, reduces only the compression lag, but has no affect on other causes of the lag.
EP 606,173 discloses a method and system for guiding a vehicle via a lagged communication channel, which comprises at the vehicle both a camera and a 3-D imager.
It is therefore an object of the present invention to provide a method and system for remotely guiding a vehicle via lagged communication channel, on which the control performance is higher than that known in the prior art under the same conditions. More specifically, it is a particular object of the present invention to provide compensations for delays due to the lagged communication channel in transferring images from the vehicle to its remote operator, and control signals from the operator to the vehicle.
It is still another object of the present invention to enable an essentially real-time control of a vehicle in a lagged communication channel, particularly when the bandwidth of the channel connecting the vehicle and the control center is narrow.
It is still an object of the present invention to perform the said vehicle guidance when the point to which the vehicle is guided is either static or moving.
It is still an object of the present invention to provide solutions to said problems in a compact, simple, and economical manner.
Other objects and advantages of the invention will become apparent as the description proceeds.